Sweet pepper plants of the species Capsicum annuum L. belong to the Nightshade family, also known as Solanaceae. It is an annual herbaceous flowering plant species native to South America.
Pepper plants are being cultivated worldwide for their highly nutritious fruits. In 2007 the acreage for sweet peppers in the United States was approximately 54.3 million, with a production of about 700,000 tons (source USDA). The pepper fruits have a high vitamin A and C content, as well as a high content in dietary fiber. They are also an excellent source of Calcium. Bell peppers are eaten raw, cooked, immature and mature and may be processed into powders, sauces, and salsas. The fruits in the unripe stage are usually green, but during ripening they usually become red, although other colors are known also such as: yellow, orange, purple, white, and brown.
Fruit color is one of the characteristics of a pepper fruit most influencing consumer preference. Therefore, optimizing and developing different fruit colors is always an important goal in breeding new pepper varieties.
There are various ways of cultivating peppers, the most common are: open field, greenhouse and shade house production. Although the species can be grown under a wide range of climatic conditions, it performs most successfully under dry and warm conditions.
When a pepper plant is cultivated under greenhouse conditions it may experience stress during very hot summers. The stress suffered by the plant may manifest itself through anthocyanin stains on the bottom of the fruits. This staining is especially visible in light colored pepper fruits such as yellow colored fruits and is not appreciated by consumers.
Tobamoviruses are a group of rod shaped viruses capable of infecting a wide array of species, including Capsicum species. Pepper infecting strains of Tobamovirus are subgrouped into ‘pathotypes’, according to their reactions on a set of differential Capsicum sp. hosts. Pathotype P0 corresponds to Tobacco Mosaic virus (TMV) and/or Tomato Mosaic Virus (ToMV), Pathotype P1 corresponds to ToMV as well. Pathotypes P1-2 and P1-2-3 belong to isolates of Pepper Mild Mottle Virus (PMMoV). Symptoms on susceptible plants can vary considerably depending on the strain of virus, time of infection, and growing conditions. Foliar symptoms include mosaicism, mottling, leaf distortion and sometimes leaf death and defoliation. Fruits of infected plants may be undersized, deformed, mottled or blotched and have a rough surface. Infected seedlings are usually stunted and pale. Tobamoviruses are easily transmitted through contact and can be transmitted by seed. Tobamoviruses can especially in greenhouse cultivation be a problem due to the higher plant density compared to open field cultivation. Tobamoviruses are responsible for significant economic losses in pepper production areas. Genetic resistance to Tobamoviruses is thus highly desired.
The plant architecture of pepper varieties has been optimized through breeding to meet different methods of cultivation. In open field cultivation a closed plant type is preferred in order to prevent damage to the plant and fruits. In covered cultivation such as greenhouse and plastic tunnel cultivation such a closed plant type is not necessary. In covered cultivation a more open plant type is desired, because this better facilitate the development of the fruits, and makes the harvesting of fruits less labor intensive, both being very beneficial for a grower.
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